1. Field of the Invention
The present invention relates to a facsimile machine and a facsimile communication system for carrying out facsimile communication via a communication network, such as a packet communication network, which differs from a public telephone network.
2. Description of the Related Art
A communication procedure between facsimile machines connected to the telephone network is regulated by the ITU-T (International Telecommunication Unionxe2x80x94Telecommunication Standardization Sector) Recommendation T. 30. In this communication procedure, after a call is set, image data is transmitted and received between facsimile machines while given control signals are exchanged in order. For confirming whether the communication is normally executed, each of the facsimile machines monitors whether a response signal is received from the counterpart facsimile machine within a given time in response to a certain signal transmitted thereto. If no such a response signal is received within the given time, the foregoing certain signal is retransmitted to the counterpart facsimile machine. Then, if no such a response signal is received even after given number times repetition of the retransmission, the facsimile machine judges that a transmission failure has occurred, and forcibly stops or interrupts the communication with the counterpart facsimile machine.
In recent years, following the rapid spread of the Internet, a communication procedure for realizing facsimile communication via the Internet has been proposed. Facsimile machines are connected to the telephone network, while the telephone network is connected to the packet communication network forming the Internet via gateways.
One of the facsimile machines is connected to one of the gateways via the telephone network, while another facsimile machine is connected to another gateway via the telephone network. The gateways are connected to each other via the packet communication network.
Between the facsimile machine and the gateway connected thereto via the telephone network, communication is carried out pursuant to the communication procedure regulated by the ITU-T Recommendation T. 30. On the other hand, between the gateways connected via the packet communication network, communication is carried out pursuant to a communication procedure regulated by the ITU-T Recommendation T. 38.
The conventional communication technique, however, has the following problem to be solved.
Since the packet communication network deals with a large number of communications at a given frequency band, if the traffic amounts increase, it is possible that large communication delays are generated locally. Thus, it is possible that a significant communication delay occurs between the gateways while facsimile communication is executed. If a communication delay occurs between the gateways, such a communication delay is transferred, as it is, to the telephone network connecting between the facsimile machine and the gateway. According to the communication procedure regulated by the ITU-T Recommendation T. 30, if a communication delay larger than a given value is generated, it is judged that a communication failure has occurred so that facsimile communication is forcibly interrupted.
FIG. 19 is a sequence diagram showing an example wherein facsimile communication is interrupted due to a communication delay caused between gateways.
In this example, when the line connection is established through an exchange of various control signals after a call is made, image data is transmitted from a calling facsimile machine to a calling-side gateway. The image data should then be transmitted from the calling-side gateway to a called-side gateway and further transmitted from the called-side gateway to a called facsimile machine.
Following the transmission of the image data, the calling facsimile machine transmits an EOP (End of Procedures) signal and then goes into a standby state awaiting an MCF (Message Confirmation) signal to be sent from the called facsimile machine in response to the EOP signal.
However, if a large communication delay is caused in the packet communication network connecting between the calling-side gateway and the called-side gateway, the image data transmitted from the calling-side gateway is received, but being largely delayed, at the called-side gateway. Thus, it is possible that the called facsimile machine can not receive the image data within a lapse of a given time from the transmission of the image data by the calling facsimile machine.
If that happens, the MCF signal from the called facsimile machine can not be received at the calling facsimile machine within a lapse of, for example, three seconds from the transmission of the EOP signal as regulated by the communication procedure. In this case, the calling facsimile machine retransmits the EOP signal twice at intervals of three seconds.
If the MCF signal from the called facsimile machine is not received even after two-times retransmission of the EOP signal, the calling facsimile machine judges that a communication failure has occurred, and transmits a DCN (Disconnect) signal for forcibly interrupting the communication.
Since the communication is forcibly interrupted due to an occurrence of the foregoing communication delay, the communication can not be rendered smooth and reliable.
Therefore, it is an object of the present invention to provide a facsimile machine and a facsimile communication system which can achieve smooth and reliable communication by reducing a possibility of communication errors caused by a communication delay.
It is another object of the present invention to provide a facsimile machine and a facsimile communication system which can reduce a possibility of communication errors caused by a communication delay between gateways.
According to one aspect of the present invention, there is provided a facsimile machine comprising a timing monitor section having a timer for setting a timer value representing a maximum allowable response time for a response signal to be received from a counterpart facsimile machine, the timing monitor section monitoring whether the response signal is received from the counterpart facsimile machine within the timer value; a timer value change information transmitting section which transmits first timer value change information, possessed by the subject facsimile machine, to the counterpart facsimile machine; a timer value change information detecting section which detects second timer value change information transmitted from the counterpart facsimile machine, the second timer value change information selected from the first timer value change information at the counterpart facsimile machine; and a timer value changing section which changes the timer value using the second timer value change information.
According to another aspect of the present invention, there is provided a facsimile machine comprising a timing monitor section having a timer for setting a timer value representing a maximum allowable response time for a response signal to be received from a counterpart facsimile machine, the timing monitor section monitoring whether the response signal is received from the counterpart facsimile machine within the timer value; a timer value change information detecting section which detects timer value change information transmitted from the counterpart facsimile machine, the timer value change information possessed by the counterpart facsimile machine; a timer value change information selecting section which selects, from the timer value change information detected at the timer value change information detecting section, optimum timer value change information to be used in facsimile communication to follow, the optimum timer value change information commonly possessed by the subject facsimile machine; a timer value change information transmitting section which transmits the optimum timer value change information to the counterpart facsimile machine; and a timer value changing section which changes the timer value using the optimum timer value change information.
It may be arranged that the facsimile machine further comprises a communication mode selecting section which selects, upon calling, a communication mode for implementing facsimile communication with the counterpart facsimile machine via a communication network other than a telephone network, wherein the timer value change information detecting section detects the timer value change information only when the communication mode is selected at the communication mode selecting section.
It may be arranged that the facsimile machine further comprises a dial number storage section which stores dial numbers of counterpart facsimile machines to which facsimile communication is to be implemented via the communication network; and a dial number search section which, when a dial number is inputted, searches the dial number storage section for the inputted dial number, wherein the communication mode selecting section selects the communication mode when the inputted dial number is located in the dial number storage section.
It may be arranged that the dial number storage section further stores optimum timer value change information for each of the counterpart facsimile machines such that the dial number and the corresponding optimum timer value change information are mutually retrievable from each other, and that, when the inputted dial number is located in the dial number storage section by the dial number search section, the timer value change information selecting section selects the stored timer value change information corresponding to the located dial number.
According to another aspect of the present invention, there is provided a facsimile communication system comprising a calling facsimile machine; a calling-side gateway connected to the calling facsimile machine via a telephone network; a called-side gateway connected to the calling-side gateway via a communication network other than the telephone network; and a called facsimile machine connected to the called-side gateway via the telephone network, wherein the called facsimile machine comprises a timer for setting a first timer value representing a maximum allowable response time for a response signal to be received from the calling facsimile machine; a called-side timer value change information transmitting section which transmits first timer value change information, possessed by the called facsimile machine, to the called-side gateway; a called-side timer value change information detecting section which detects second timer value change information transmitted from the called-side gateway, the second timer value change information selected from the first timer value change information at the called-side gateway; and a called-side timer value changing section which changes the first timer value using the second timer value change information, wherein the calling-side gateway comprises a called/calling communication delay estimating section which estimates a delay time of a signal transmitted from the called-side gateway to the calling-side gateway; a first calling-side timer value change information detecting section which detects the first timer value change information received from the called-side gateway; a first calling-side timer value change information selecting section which, based on the delay time, selects from the first timer value change information first optimum timer value change information to be used in facsimile communication to follow; and a timer value change information replacing section which replaces the first timer value change information with the first optimum timer value change information so as to transmit the first optimum timer value change information to the calling facsimile machine, and wherein the calling facsimile machine comprises a timer for setting a second timer value representing a maximum allowable response time for a response signal to be received from the called facsimile machine; a second calling-side timer value change information detecting section which detects the first optimum timer value change information received from the calling-side gateway; a second calling-side timer value change information selecting section which selects from the first optimum timer value change information second optimum timer value change information to be used in facsimile communication to follow, the second optimum timer value change information commonly possessed by the calling facsimile machine; a calling-side timer value change information transmitting section which transmits the second optimum timer value change information to the calling-side gateway; and a calling-side timer value changing section which changes the second timer value using the second optimum timer value change information.
According to another aspect of the present invention, there is provided a facsimile communication system comprising a calling facsimile machine; a calling-side gateway connected to the calling facsimile machine via a telephone network; a called-side gateway connected to the calling-side gateway via a communication network other than the telephone network; and a called facsimile machine connected to the called-side gateway via the telephone network, wherein the called facsimile machine comprises a timer for setting a first timer value representing a maximum allowable response time for a response signal to be received from the calling facsimile machine; a called-side timer value change information transmitting section which transmits first timer value change information, possessed by the called facsimile machine, to the called-side gateway; a first called-side timer value change information detecting section which detects second timer value change information transmitted from the called-side gateway, the second timer value change information selected from the first timer value change information at the called-side gateway; and a called-side timer value changing section which changes the first timer value using the second timer value change information, wherein the calling facsimile machine comprises a timer for setting a second timer value representing a maximum allowable response time for a response signal to be received from the called facsimile machine; a calling-side timer value change information detecting section which detects third timer value change information selected from the first timer value change information and received from the calling-side gateway; a calling-side timer value change information selecting section which selects from the third timer value change information first optimum timer value change information to be used in facsimile communication to follow, the first optimum timer value change information commonly possessed by the calling facsimile machine; a calling-side timer value change information transmitting section which transmits the first optimum timer value change information to the calling-side gateway; and a calling-side timer value changing section which changes the second timer value using the first optimum timer value change information, and wherein the called-side gateway comprises a calling/called communication delay estimating section which estimates a delay time of a signal transmitted from the calling-side gateway to the called-side gateway; a second called-side timer value change information detecting section which detects the first timer value change information received from the called facsimile machine; a called-side timer value change information selecting section which, based on the delay time, selects from the first timer value change information second optimum timer value change information to be used in facsimile communication to follow, the second optimum timer value change information selected as the second timer value change information; and a timer value change information replacing section which replaces the first optimum timer value change information received from the calling-side gateway with the second optimum timer value change information so as to transmit the second optimum timer value change information to the called facsimile machine.
According to another aspect of the present invention, there is provided a facsimile communication system comprising a facsimile machine connected to a telephone network; and a gateway connected to the telephone network and another communication network other than the telephone network, wherein the facsimile machine comprises a first timer for setting a first timer value representing a maximum allowable response time for a response signal to be received from a counterpart facsimile machine via the communication network and the gateway relative to a signal transmitted to the counterpart facsimile machine via the gateway and the communication network; and a first flow control section which re-sets the first timer to the first timer value when a re-setting command signal is received from the gateway, the re-setting command signal commanding the first flow control section to re-set the first timer to the first timer value, the first flow control section transmitting to the gateway a re-setting response signal notifying that re-setting of the first timer to the first timer value is finished, and wherein the gateway comprises a second timer for setting a second timer value corresponding to the first timer value, the second timer value representing a maximum allowable response time for the response signal to be received from the counterpart facsimile machine via the communication network relative to the transmitted signal; and a second flow control section which transmits the re-setting command signal to the facsimile machine when the response signal is not received within the second timer value, the second flow control section re-setting the second timer to the second timer value when the re-setting response signal is received from the facsimile machine, the second flow control section repeating transmission of the re-setting command signal and re-setting of the second timer to the second timer value until the response signal is received within the second timer value.
It may be arranged that the second timer value is set to be smaller than the first timer value.
According to another aspect of the present invention, there is provided a facsimile machine comprising a timing monitor section connected to a communication line and having a timer for variably setting a timer value for a response signal relative to a signal transmitted via the communication line, the timing monitor section monitoring whether the response signal is received within the timer value set in the timer; a timer value change information transmitting section which transmits timer value information via the communication line; a timer value change information detecting section which detects timer value information from a received signal via the communication line; and a timer value changing section which changes the timer value of the timer based on the timer value information detected at the timer value change information detecting section.
According to another aspect of the present invention, there is provided a facsimile communication system including a calling facsimile machine and a called facsimile machine connected to said calling facsimile via a communication line, wherein said calling facsimile machine comprises: a timing monitor section having a timer for setting a timer value representing a maximum allowable response time for a response signal to be received from said called facsimile machine, said timing monitor section monitoring whether said response signal is received from said called facsimile machine within said timer value; a timer value change information transmitting section which transmits first timer value change information, possessed by the subject facsimile machine, to said called facsimile machine; a timer value change information detecting section which detects second timer value change information transmitted from said called facsimile machine, said second timer value change information selected from said first timer value change information at said called facsimile machine; and a timer value changing section which changes said timer value using said second timer value change information; and wherein said called facsimile machine comprises: a timing monitor section having a timer for setting a timer value representing a maximum allowable response time for a response signal to be received from said calling facsimile machine, said timing monitor section monitoring whether said response signal is received from said calling facsimile machine within said timer value; a timer value change information detecting section which detects timer value change information transmitted from said calling facsimile machine, said timer value change information possessed by said calling facsimile machine; a timer value change information selecting section which selects, from said timer value change information detected at said timer value change information detecting section, optimum timer value change information to be used in facsimile communication to follow, said optimum timer value change information commonly possessed by the subject facsimile machine; a timer value change information transmitting section which transmits said optimum timer value change information to said calling facsimile machine; and a timer value changing section which changes said timer value using said optimum timer value change information.
It may be arranged that the at least a pair of facsimile machines are directly connected to a packet communication network.
It may be arranged that the timer value change information transmitting section, when working as the called facsimile machine, notifies the calling facsimile machine that the called facsimile machine is directly connected to the packet communication network and can be operated based on a timer value designated by the calling facsimile machine, and that the timer value change information transmitting section, when working as the calling facsimile machine, transmits a maximum timer value for one communication to the called facsimile machine so that an allowable communication time for one communication between the calling and called facsimile machines is regulated by the maximum timer value.
It may be arranged that the maximum timer value is selected based on an estimated communication delay in the packet communication network and an image data amount to be transmitted.